Wavelength selectable lasers are becoming important components for optical networks employing dense wavelength division multiplexing (DWDM). As the number of WDM channels increases, very tight control of emission wavelengths of lasers used in the transmitters is necessary. Transmitters having their output wavelengths selectable between specified channel wavelengths can be very useful at reconfigurable wavelength add/drop nodes. Wavelength selectable lasers can also be employed as standby transmitter sources for reliability assurance to prevent events of system failures due to transmitter failures in a DWDM system. Several wavelength-selectable lasers have been proposed for DWDM systems, including tunable semiconductor distributed-Bragg-reflector lasers, WDM laser arrays with an integrated output coupler [1], and the integrated waveguide grating multifrequency laser [2,3]. (Note that in the above and following description, a reference's identification [e.g., 2] refers to that reference's location in the Appendix) The integrated multifrequency laser utilizes an InP-based waveguide grating router (WGR) for mode selection. The passive semiconductor WGR can accurately set the channel spacing of the multifrequency laser output. Recently, fiber ring lasers using Er-doped fiber amplifiers (EDFA) as the gain medium and a silica-based WGR for wavelength selections also have been reported [4,5]. The fiber lasers can be constructed using commercially available EDFAs and silica WGRs and the lasing wavelengths are self-aligned to the bandpass wavelengths of the WGRs. However, previously reported grating-router Er-fiber ring lasers do not operate in a single mode. Because of the long fiber cavity length, there are typically 1,000 to 10,000 axial modes within the 3-dB passband of a WGR. The WGR Er-fiber ring lasers oscillate with closely-spaced (less than 10 MHz) multiple axial modes that are not resolved by an optical spectrum analyzer [5]. Such multi-mode fiber ring lasers can not be used for communications because the inter-modal optical beat noises are within the bandwidth of the receiver. What is needed is a stable single-mode wavelength selectable ring laser for use in DWDM communication systems.